Apparently persuasive impact is greatest immediately after a message is received. The impact receeds in impact thereafter. This of course varies depending on the message and the credibility of the source (page 34 Input/Output).

MEDIA p 36

Because people switch channels when ads come on TV, public service announcements could be more effective if incorporated into the program (It’s not easy being green).(McGuire 1984 Piotrow 1990)

People are more persuaded by messages when alone (Keating & Latane 1976)

RESISTANCE

Campaigns can also try to influence people to resist the persuasions of things like cigarette advertisements. McGuire says that there are six things that can help influence this resistance:

Having the person publicly express their position (he quotes Lwein’s 1951 world war II group decision research here);

Affecting emotional states such as anger, self-esteem or anxiety (fear based messages or positive ones);

“Anchoring the person’s initial stand on the issue to another person’s beliefs or values”, especially someone they respect;

Educate people in critical thinking (but can backfire as people who are more educated can also be more persuadable, see Sente notes);

Show people examples of other people resisting (“unyeilding models)

Expose people to weaker innoculation messages so that when exposed to stronger messages they will already have in-built defenses.

McGuire says that this is overly simplistic and in fact, multiple paths exist in the process. Sequentiality is not guaranteed. People might jump from say number 7 to number 11 (“when people form their attitudes to justify their behavior”). See also the Health Belief Model.